Live production of a television program such as a news show often requires one or more television cameras to capture the image of different “on-air” talent, such as a news anchor, weather reporter and/or sports reporter. In the past, a camera operator would manually operate each television camera. Such manual operation often entailed moving the camera to different positions within a television studio to make sure that the particular on-air talent appeared in the center of the camera's field of view. During broadcasting, the on-air talent often will make slight lateral movements, forcing the camera operator to displace the camera by a corresponding amount to maintain the on-air talent within the center of the camera's field of view. The camera operator will generally observe the image of the on-air talent in the camera's view finder so the operator will have immediate knowledge of the movement of the talent and move the camera accordingly.
Advances in technology have led to the development of robotic television cameras, such as the “Cameraman”, available from Thomson Grass Valley, Jacksonville, Fla. Such robotic cameras operate under the control of one or more computers which manage functions such as camera displacement along the x, y, and z axes, pan, tilt, zoom and focus. By appropriately programming the computer(s), the camera will operate automatically, thus obviating the need for manual control. Typical robotic cameras have the ability to move from a known home position to one or more pre-set positions, each pre-set position enabling a particular camera shot of an on-air talent. Generally, the pre-set camera positions remain static. In other words, if the on-air talent moves even slightly to the right or left while the robotic camera remains static, then the on-air talent will appear off-center within the field of view of the camera.
To overcome this difficulty, robotic cameras can include automatic tracking technology such as such the tracking system described in U.S. Pat. No. 5,668,629 issued in the name of Jeffrey Parker et al. The automatic tracking system described in the '629 patent employs a Infra-Red (BR) transmitter carried by the moving object (e.g., the on-air talent) for transmitting signals to an IR receiver carried by the robotic camera. By detecting the deviation in the signal transmitted by the transmitter as it moves with the object, the IR receiver can establish the new position of the moving object and provide that information to the computer(s) controlling the robotic camera to displace the camera accordingly.
The IR tracking technology described in the '629 patent works well for tracking a single moving object. However, tracking of multiple objects can prove problematic, such as in the case when a single robotic camera serves to capture the image of several different on-air talent, as occurs when the camera moves to capture the image of a news anchor at one instant, and a weather reporter at a different instant. Each different on-air talent would need to carry a separate IR transmitter to avoid interference, thus necessitating the need for multiple IR receivers on the camera. This IR system also suffers from the disadvantage that the anchor person has to wear an embedded system that should be located at the center of the head to have an accurate estimate of the head position
Thus, a need exists for a tracking technique that overcomes the aforementioned disadvantage of the prior art.